These studies are directed toward understanding the molecular basis of the control of cellular differentiation and its relationship to malignancy. Mouse erythroleukemia cells provide an excellent model system for this type of investigation since they undergo erythrodifferentiation to a hemoglobin-producing stage in tissue culture and in vivo. This differentiation is stimulated in vitro by dimethyl sulfoxide and other compounds. Many of these compounds are not structurally related. The induction of hemoglobin production by several of the inducers is accompanied by an increase in single-stranded breaks in DNA. Therefore the effects of several of the inducing compounds on DNA metabolism and structure in "wild-type" and variant cell lines is being studied.